1. Field of the Invention
The present invention relates to an X-ray diffraction apparatus allowing X-ray diffraction measurement of a sample to be carried out with the use of plural kinds of characteristic X-rays emitted by plural kinds of target materials.
2. Description of the Related Art
An X-ray diffraction apparatus allowing X-ray diffraction measurement of a sample to be carried out with the use of plural kinds of characteristic X-rays emitted by plural kinds of target materials is disclosed in Japanese patent publication No. 11-304728 A (1999) which is referred to as the first publication hereinafter. The first publication discloses, for a start, a rotating-anode X-ray tube which generates plural kinds of characteristic X-rays. The rotating-anode X-ray tube has two kinds of target regions made of Co (cobalt) and Cu (copper) respectively. Regarding how to arrange the two target regions, plural embodiments are disclosed, one of which is an arrangement in that Co and Cu are sectioned in a direction parallel to an axis of rotation of the rotating anode as shown in FIG. 3 of the present application. The upper part of the rotating anode emits the characteristic X-ray of Co, while the lower part emits the characteristic X-ray of Cu. The first publication further discloses X-ray diffraction measurement of a sample with the use of such two kinds of characteristic X-rays. That is, a monochromator is arranged between the X-ray tube and the sample, the monochromator consisting of an upper half having a multilayer film thereon allowing only the Co characteristic X-ray to be reflected and a lower half having another multilayer film thereon allowing only the Cu characteristic X-ray to be reflected. Between the sample and an X-ray detector is arranged a Soller slit for restricting the vertical divergence of X-ray. The X-ray detector is a scintillation counter. With a combination of the monochromator and the Soller slit, the Co characteristic X-ray passes through the upper half of the X-ray path almost in a parallel beam form, while the Cu characteristic X-ray passes through the lower half of the X-ray path almost in a parallel beam form. When intending to carry out X-ray diffraction measurement of the sample using the Co characteristic X-ray, the lower half of the X-ray path is shut off by a shutter which is arranged between the monochromator and the sample, so that only the Co characteristic X-ray is incident on the sample. On the other hand, when intending to carry out X-ray diffraction measurement of the sample using the Cu characteristic X-ray, the upper half of the X-ray path is shut off by the shutter, so that only the Cu characteristic X-ray is incident on the sample. Thus, the X-ray diffraction measurement of the sample using the two kinds of characteristic X-rays becomes possible.
Additionally, the present invention is also concerned with X-ray diffraction measurement of the sample using a position-sensitive X-ray detector. Electronic recording of a diffracted X-ray using the position-sensitive X-ray detector, specifically a two-dimensional CCD sensor, is disclosed in Japanese patent publication No. 2005-91142 A, which is referred to as the second publication hereinafter. The second publication discloses that a two-dimensional CCD sensor of the FFT (Full Frame Transfer) type is allowed to execute the TDI (Time Delay Integration) operation, making it possible to carry out high-speed, high-sensitive X-ray diffraction measurement.
As has been disclosed in the first publication, if using an X-ray tube which can emit two kinds of characteristic X-rays, it is possible to carry out X-ray diffraction measurement of a sample using the two kinds of characteristic X-rays. It is impossible, however, in the first publication to carry out X-ray diffraction measurement of a sample at the same time with the use of the two kinds of characteristic X-rays, because the shutter allows only any one of the characteristic X-ray to be incident on the sample. If the shutter is fully opened to allow the two kinds of characteristic X-rays to be incident on the sample at the same time, the scintillation counter will receive at the same time both the diffracted X-ray of the Co characteristic X-ray from the sample and the diffracted X-ray of the Cu characteristic X-ray from the sample, making it impossible to separately detect the two kinds of diffracted X-rays.